Question

Explain the relationship between Earth’s ancient atmosphere and the evolution of some of the first life forms on Earth by selecting the most accurate of the provided descriptions. Use the terms anaerobic and phototrophic correctly, and accurately reflect the effect of cyanobacteria on the atmosphere.

a) Anaerobic conditions led to the evolution of phototrophic organisms like cyanobacteria, which altered the atmosphere by releasing oxygen.
b) Phototrophic conditions led to the evolution of anaerobic organisms like cyanobacteria, which altered the atmosphere by removing oxygen.
c) Anaerobic conditions led to the evolution of non-phototrophic organisms like cyanobacteria, which altered the atmosphere by reducing nitrogen levels.
d) Phototrophic conditions led to the evolution of anaerobic organisms like cyanobacteria, which altered the atmosphere by increasing carbon dioxide levels.

Answer 1

During the first two billion years, the Earth's atmosphere had no molecular oxygen, enabling anaerobic organisms to thrive.

Step-by-step explanation:

The relationship between Earth's ancient atmosphere and the evolution of some of the first life forms on Earth is as follows:

During the first two billion years of Earth's existence, the atmosphere was anoxic, meaning there was no molecular oxygen. This anaerobic condition allowed only anaerobic organisms to live. Phototrophic organisms, which convert solar energy into chemical energy, appeared within one billion years of Earth's formation. Cyanobacteria, also known as blue-green algae, evolved from these phototrophs and began the oxygenation of the atmosphere by releasing oxygen as a by-product of photosynthesis.

This increase in atmospheric oxygen concentration allowed the evolution of more efficient oxygen-utilizing catabolic pathways and enabled the colonization of land. The presence of oxygen also led to the development of ozone, which absorbs harmful ultraviolet light. Ultimately, the increase in oxygen concentrations allowed the evolution of other life forms.